Transmission Output Seal/flange

David's8 · #1 16th July 2015, 06:42 PM

"Borrowed" my local indie's lift to inspect a potential leak in the exhaust (which was confirmed!) but then I noticed oil leakage from the rear transmission output seal -

. As the exhaust joint forward of the cats is leaking it seems sensible to get both jobs done at the same time. It was done back in Aug 2010 when The Laird had the car but the flange wasnt done at the time due to the delivery time for the flange. Given that the seal has lasted 60k/5 yrs and the cost of a new flange being north of £150 whats the advice about replacing just the seal?

notorious · #2 17th July 2015, 06:51 AM

I've replaced flange and seal about two years ago at Chester transmissions.
But it now leaks again. Well, not exactly leaks, but the area is not 100% dry there. I can only suggest to replace everything again.

You live close to Mackie's so you're in great position to do this

They should have flange available otherwise preorder.

I think I'll wait for a serious gearbox repair, remove it and reseal it completely.

The_Laird · #3 17th July 2015, 07:08 AM

I had the seal and flange replaced ay Mackies last year when I had the gearbox serviced.

But, it's expensive! IIRC, the total bill was around £500 with the gearbox service, seal, flange, labour and VAT.

If just a seal replacement lasted 5 years/60K miles and Sergey's 'proper job' only lasted 2 years, I think I know what I'd be tempted to do!

andycaca · #4 17th July 2015, 07:34 AM

i had the seal replaced by a friendly mechanic. he only had to remove the passenger side cat to get access. the seal recesses 1.7mm from the surface, be very careful and gentle when replacing it

also, you will need to replace the oil when the seal is back in.

David's8 · #5 17th July 2015, 07:47 AM

Thanks for the replies. My plan is to get the exhaust job and the seal replaced at the same time but leave the flange as is. i have printed off the section from the service manual ref the procedure/distances/tolerance and oil quantities which I will give to the mechanic.

ainarssems · #6 17th July 2015, 10:20 AM

I replaced seal only on mine 2 years ago and i pushed it in too much before realizing it. As it's impossible to get it out without damaging and I did not wait for another seal I assembled it and though we'll see how it goes and replace again when it starts leaking. So far so good, now only the side seals where front driveshafts come out start leaking a bit.

If I need to replace it again it's no brainer - seal only for me. Original lasted 16 years and 130k with the old style flange so why would not replacement last just as long if done correctly and if there is no damage to the old flange. Seals do fail even on boxes that had new flange from factory. I will just be more careful not to push it in too much next time, maybe also try aftermarket Viton seal now that I got seal measurements from the first time.

But I do it myself and don't need to worry about paying for the labour again if it fails soon. For others it might give a bit more piece of mind if you replace flange as well to prevent it failin soon and paying for job again or to have less downtime while car is being repaired. But like I said seals do fail even on the boxes that had new flange from the factory so I am not sure how much or if any extra miles new design offer.

Goran · #7 17th July 2015, 10:48 AM

I think my original old-type seal lasted a long time too. The only reason it leaked again within a year or less of replacement is that some genius (supposed transmission specialists) who I took it to, replaced it with the new type seal into the old flange. That clearly does not work. Had they replaced it with old-type seal I might have been fine but in the end took it to my local specialist who replaced with new flange and seal.
So watch out for that, if you take it to an independent who doesn't know. Make sure tell them "old type seal please"

David's8 · #8 17th July 2015, 11:08 AM

Quote:

Originally Posted by Goran

I think my original old-type seal lasted a long time too. The only reason it leaked again within a year or less of replacement is that some genius (supposed transmission specialists) who I took it to, replaced it with the new type seal into the old flange. That clearly does not work. Had they replaced it with old-type seal I might have been fine but in the end took it to my local specialist who replaced with new flange and seal.
So watch out for that, if you take it to an independent who doesn't know. Make sure tell them "old type seal please"

Thanks Goran. I had noted that and have the part numbers - both Audi and ZF - from another thread (thanks Ainars) so that they get the right one. i.e.
018 409 399B /ZF 0734 319 588. The modified one is 01V 409 399A and the modded flange 01V 409 809A.

Mechcanico Lee · #9 26th July 2015, 12:24 PM

Couple of thoughts on this , just in general ...

Does the auto box have a breather valve , is it clear
The gearboxes that re occur and leak again could it be a fluid boil condition that creates gas build up pressure which escapes at the easy point .. ie gearbox out put seal .
I also understand that it could be a design flaw .

Years ago we had a old v6 Granada that when the owner towed his caravan up some big hill the box would leak from the torque converter seal , this was replaced but it leaked again whenever the caravan was on tow .

We fitted an air fed gearbox oil cooler and it never leaked again after that , this was in the days when the only auto trans oil was the dextron

Adrian E · #10 26th July 2015, 01:10 PM

The rear seal leaks diff oil rather than gearbox - only holds about 1 litre but makes a hell of a mess when it is leaking even fairly lightly. Don't think there's any breather on it?